The present invention relates to railway vehicle couplers and more particularly to an improved railway coupler head having knuckle pin retaining means that are free to fully rotate with the knuckle pin.
Both AAR Type E and Type F railway coupler heads are known to have knuckles which interface with and receive the transferred draft load from opposing knuckles of mating coupler heads. Further, both type coupler heads are known with a knuckle pin which passes through an aperture having a circular cross-section in the knuckle as well as through aligned apertures having elongated non-circular cross-sections in the upper and lower pivot lugs on either side of the knuckle. The knuckle pin serves to secure the knuckle to the coupler head while allowing for the knuckle to pivot between an open and closed position.
The knuckle pins are currently retained within the aligned apertures by a cotter pin which passes through a transverse hole in the bottom portion of the knuckle pin that extends downwardly from the bottom surface of the lower pivot lug. Such a retention device is shown in Altherr, U S. Pat. No. 3,627,145. When the knuckle pin moves upwardly during use, the cotter pin comes into contact with the bottom surface of the lower pivot lug precluding against any further upward movement which would result in the unintentional removal of the knuckle pin.
A problem that has occurred with the current arrangement for retaining the knuckle pin is that, as the knuckle pin turns initially within the aligned apertures of the pivot lugs, the cotter pin contacts and becomes caught upon a flange section of the coupler head which protrudes downwardly from the bottom surface of the lower pivot lug in close proximity to the bottom portion of the knuckle pin in which the cotter pin is received. The cotter pin, while caught upon the downwardly protruding flange section, restricts any further rotation of the knuckle pin within the pivot lugs. Thus, the cotter pin actually prevents rotation of the knuckle pin.
Excessive knuckle pin failures have been experienced on a plane perpendicular to the knuckle pin axis at the longitudinal position along the knuckle pin between the knuckle and the upper pivot lug. This position is the most vulnerable due to the fact that there is a small slack gap between the knuckle and the upper pivot lug during use as the knuckle rests on the lower pivot lug. This slack gap, combined with the absence of knuckle pin rotation caused by the cotter pin, creates an area of point stress on the knuckle pin which results in a reduced fatigue life for the knuckle pin.